1. Field of the Invention
This invention relates to a portable mixing recorder which enables a user to produce music by inputting an audio signal via a microphone or the like while monitoring a recorded audio signal, and mixing the input audio signal and the recorded audio signal, as well as to a method and a program for controlling the portable mixing recorder.
2. Description of the Related Art
In recent years, musical apparatuses with enhanced portability have been realized due to the advance of the audio compression technique and the miniaturization technique of electronic components. For example, a portable MP3 player employs the audio compression technique of MP3 (MPEG-1 Audio Layer-III), and reproduces audio signals encoded in the MP3 format. In the MP3 player, a WAV file obtained by digitally sampling an audio signal from the performance of a musical piece and/or the singing of a song is encoded in the MP3 format, and the resulting file compressed in the MP3 format is stored in a flash memory or the like. This enables the user to enjoy the reproduction of the recorded musical piece and/or song, away from home, e.g. outdoors, by using the portable MP3 player. Further, a portable karaoke apparatus is disclosed e.g. in Japanese Laid-Open Patent Publication (Kokai) No. 2000-338984 is capable of extending and reproducing an audio signal file encoded and stored in the MP3 format, and at the same time mixing an audio signal of a human voice input via a microphone with the reproduced audio signal, for audio reproduction, thereby enabling users to enjoy a desired karaoke performance away from home.
These apparatuses are all intended for reproduction or playback, and do not record or store audio signals input via a microphone or the like. However, there have been also proposed other types which are capable of recording and storing audio signals. For example, there has been proposed a portable MP3 recorder which is equipped with an analog input terminal, and is capable of performing A/D conversion of an audio signal input via the analog input terminal from a cassette tape recorder, a radio, or the like, and then encoding the resulting digital audio signal in the MP3 format, to store the compressed file as an audio signal file.
However, the portable MP3 recorder is not capable of performing “recording with mixing (overdubbing)” in which a number of input signals are multiplexed. As a musical apparatus capable of mixing, a double radio-cassette player, for example, is known. In the double radio-cassette player, it is possible to reproduce musical tones from one cassette tape, and at the same time mix an audio signal of the reproduced musical tones and an audio signal input via a microphone or an external input terminal, to record the mixed audio signals in the other cassette tape in a multiplexing manner.
In general, when music production e.g. by overdubbing is to be performed away from home, it is necessary for a musical apparatus to have capabilities of recording and mixing sound signals while maintaining the quality of the resulting mixed sound signal. However, the portable MP3 player and the karaoke apparatus are dedicatedly designed for reproduction, and not capable of recording input audio signals, while the portable MP3 recorder is not capable of mixing. Therefore, none of them is suitable for music production. Further, in the double radio-cassette player, when the mixing is repeatedly carried out, dubbing of analog signals of musical tones is repeatedly carried out, resulting in seriously degraded sound quality of the resulting audio signal file. Therefore, this apparatus is not suitable for music production, either.
On the other hand, a 4-channel MD multi-channel recorder using an MD (Minidisk) has been proposed (in Japanese Laid-Open Patent Publication (Kokai) No. 8-77757) as an apparatus designed mainly for music production. This multi-channel recorder is capable of recording a line-input signal on an MD after A/D conversion and audio compression. For example, the recorder is capable of overdubbing musical tones of several parts, mixing the musical tones, and then temporarily moving the mixed sound to a free channel (ping-pong recording). If a large number of parts are to be processed, musical tones of still another part can be further recorded in a channel made free by the ping-pong recording. Finally, all the parts can be mixed down in all the four channels.
However, in the above multi-channel recorder, during ping-pong recording, a digital audio signal recorded on the MD is converted to an analog audio signal and then mixed with a line-input signal (analog audio signal), and hence when the ping-pong recording is repeatedly carried out, the sound quality is inevitably degraded. Further, the multi-channel recorder is a stationary type which is not suitable for use in music production away from home.
Moreover, in the above multi-channel recorder, whether a line-input audio signal may be recorded in a single channel of an MD or whether audio signals recorded in a plurality of channels of the MD may be mixed and recorded in another channel by ping-pong recording, a recording instruction is given using a single recording key.
However, when the single recording key is used for issuing both an instruction for normal recording (i.e. recording of a line-input audio signal in a single channel) and the instruction for ping-pong recording, a user cannot visually distinguish the two instructions from each other and the user hesitates in determination as to what operation to do next.
Further, as shown in FIG. 13, when the above-described multi-channel recorder is used for carrying out overdubbing (recording with mixing) of a line-input audio signal (performance signal) on part of an audio signal (source file) recorded in a channel, it is necessary to start the operation of the recording with mixing simultaneously with the start of reproduction of the source file, stand by while monitoring reproduction of the source file until the recording proceeds to a desired position for starting the overdubbing, and then start performance for the overdubbing, at the time point the recording has come to the position.
However, when a performance signal to be overdubbed is captured via line input by collecting, via a microphone, performance tones generated by a user playing a musical instrument, the microphone can pick up undesired tones or noise other than the performance tones, so that the user has to be very careful so as not to make noise while waiting to play the instrument, which causes the user to lose concentration on the performance.